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COPYRIGHT DEPOSUi 

















































How the 

WORLD is CHANGING 


UNIFORM WITH THIS VOLUME 


HOW THE WORLD BEGAN 

The Story of the Beginning of Life on Earth 

HOW THE WORLD GREW UP 

The Story of Man 

HOW THE WORLD IS RULED 

The Story of Government 

THE WORLD OF ANIMALS 

The Story of Animals 

THE GARDEN OF THE WORLD 

The Story of Botany 

THE WORLD’S MOODS 

The Story of the Weather 

THIS PHYSICAL WORLD 

The Story of Physics 

WHAT MAKES UP THE WORLD 

The Story of Chemistry 

OTHER WORLDS THAN OURS 

The Story of Astronomy 


Thomas S. Rockwell Company 
Publishers 

CHICAGO 








II 


Publishers’ Note 

This book presents in popular form the 
present state of science. It has been reviewed 
by a specialist in this field of knowledge. An 
excerpt from his review follows: 

”This boo\ contains, in my opin¬ 
ion, a very clear and accurate state¬ 
ment of geological processes, and 
should prove very interesting reading 
to anybody who wishes to add one 
of the most important chapters of 
the earth sciences to his stoc\ of 
natural philosophy.” 


Signed: Adolf Carl Noe 

Associate Professor 
The Department of Geology 
The University of Chicago 








Squeezing the continents caused their borders to 
wrinkle up into the mountain chains 














HOW THE 

WORLD IS CHANGING 


THOMAS 


By 

Edith Heal 5 enieY' 

Drawings by 
Terry Smith 


S. ROCKWELL COMPANY 

CHICAGO 

1930 


ltO« 


at* 1 * 


Copyright, 1930, by 

THOMAS S. ROCKWELL COMPANY 

CHICACO 




Printed in United States of America 








©Cl A 30111 


CONTENTS 


This Changing World 13 

I The Lands 15 

What covers the earth? What is soil? What 
is gravel? What is a boulder? What is sand? 
What is dust? Where do sand dunes come 
from? What shape are they? How do they 
travel? What is a desert? What is a cold 
desert? What is an oasis? What are wind- 
ripples? How does sand carve rock? Why 
is a pebble round? How does a pebble tell 
where it has been? What makes the moun¬ 
tains? How are mountain pea\s formed? 
What is a hill or a butte? Why do shore¬ 
lines change? How are sea-caves made? 
What is a sea-cliff? How are capes and off¬ 
shore islands formed? How are great islands 
formed? What is a valley? Why is a valley 
crooked? What is a tributary valley? In 
what other way can a valley be made? How 
does a valley change as it grows old? How 
can a valley keep from turning into a river? 
What are gorges and canyons? What are 
caverns? What is a volcano? What causes 
an earthquake? Where is an earthquake 
likely to occur? What are some of the effects 
of earthquakes? What causes a landslide? 

Can land be struck by lightning? How is 
land lost? 


II The Waters 

Where did the oceans come from? What 
does the ocean bottom loo\ li\c? What 
corresponds to mantle roc\ under the sea? 
What are the colored muds? What are the 
oozes? What accidental deposits have been 
found? What are the measurements of the 
ocean? What maizes the ocean salty? What 
is a shallow sea? What is the life of the 
ocean world li\e? What influences affect the 
ocean? How is a bay formed? How are 
la\es made? What are salt la\es? What 
is a marsh? What is ground water? What 
happens to ground water? What is a geyser? 
What is a river? How are waterfalls formed? 
What is a delta? What accidents may happen 
to a river? What is a snow field? What is 
a glacier li\e? What is a aevasse? How 
does a glacier affect the land surface? What 
is an iceberg? What were the ancient glaciers 
li\e? What is the importance of water? 

III The Inside of the Earth 

What would the earth loo\ li\e if it were cut 
in half? Is the inside of the earth hot? 
What are the principal classifications of rocJ(? 
What are the four great series of sedimen¬ 
tary roc\s? Why are there no fossils in 
igneous roc\s? What is decayed roc\? 
What causes the coloring in roc\s? How are 
crystalline roc\s formed? Why is a granite 
building li\e a precious jewel? Why are 
some of the crystals more precious than 


others? What colors precious stones? What 
is the romance of a gem? How were the 
stratified roc\s made? What is an adobe 
house? What two building materials are 
closely related? What is gold and silver? 
What is coal? What are the different fffnds 
of coal? What is petroleum? How are iron 
ore-beds formed? What is chal}(? Where 
does salt come from? What is the greatest 
mystery of the earth? 

IV The Effect of the Earth on Man 

Can man change the earth? Why are there 
more people in the Northern Hemisphere 
than in the Southern? How have mountains 
influenced men? What are mountain passes? 
What do the mountains offer men? What 
is the importance of the lowlands? What 
fffnds of plains are thei e? How have valleys 
taf^en part in human history? What role 
does an island play? Where is most import¬ 
ant city on nearly every continent located? 
What is the advantage of a drowned coast? 
How does the soil direct mans activity? 
How are cities born? What occupations does 
the earth offer man? What is life dependent 
upon? How did the ocean become a high¬ 
way? How does the ocean water the soil? 
What is the importance of waterways? How 
does climate affect man? What are the gifts 
of the inland waters? Why is the United 
States the fortunate child of the earth? 







LIST OF ILLUSTRATIONS 


Squeezing the continents caused their borders to wrinkle 
up into the mountain chains 4 

Soil contains certain minerals and food for plants 17 

Reindeers are the steeds of the cold desert 22 

Water slowly excavates caves. If the cliff is low, the 
water often forms an opening in the roof 31 

An old valley has gentle slopes because as it gets older 
the water begins to wear down the sides 34 

A strange, dim green world of plants with extraordinary 
fish swimming about 45 

Old Faithful in Yellowstone Park erupts regularly every 
hour or so 51 

The water falls over the high rocks 55 

Icebergs float like mysterious boats over the water 59 

Crystals formed from the minerals in crystalline rock 7 1 
In Mexico, houses are often built of fine-grained ma¬ 
terial called adobe 77 

The hidden layers of plants became coal 81 

The oil fields are immensely valuable to man 83 

Hot steam may burst forth 88 

The grasslands of mountains are natural pasture grounds 95 
Islands have tempted men to explore—to leave the se¬ 
curity of the mainland 99 

After these early voyages the terrors of the ocean began 
to lessen 107 





















THIS CHANGING WORLD 


T HE world will continue to change as long 
as it endures. In this way it resembles our 
own span of life which is marked by growth 
and change from the beginning until the end. 
Like all growing things, the world shows the 
effects of its tremendous changes. In its fea¬ 
tures may be read the history of slow move¬ 
ments and churnings and the furious onslaught 
of the elements throughout past ages. It is like 
a sensitive body shaped by the touch of wind, of 
rain, of heat, of cold, and the weight of pressures 
that bear down upon it; torn and furrowed by 
the mysterious upheavals within its sphere—the 
rising of hot melted rock to the surface or the 
violent shifting and slipping of the layers of 
rocks beneath. 

There is no permanence. The waves are 
never still; the sands move; the rain-washed 
soils are swept away. Eternal change follows 
endless turmoil and constant movements go in 
slow cycles or come like sudden accidents. 


13 















V 


. 

' 




























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* 














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I 


THE LANDS 

M OST of the land is covered by mantle 
rocl{. Mantle rock received its name 
because it forms a mantle covering the solid 
underlying rock. Mantle rock is the part of this 
solid rock that has been exposed and has been 
broken up into loose material by rain, tempera¬ 
ture changes, ice, wind, and chemicals in the air. 

According to the changes and chemicals of 
the air, the amount of water and the effects of 
minerals that come in contact with mantle rock, 
it may change its form to clay, sand, earth, soil, 
gravel or loose rock. 

Sometimes when the surface slope of the 
earth is steep, the loose mantle rock is washed 
away and the solid rock appears, as on the slopes 
of mountains or cliffs that face the sea. 

The upper surface of mantle rock is called 
is 


What covers the 
earth? 


What is soil? 


What is gravel? 


What is a 
boulder? 


What is sand? 


16 HOW THE WORLD IS CHANGING 

soil and is usually from two or three inches to 
several feet deep. Soil contains certain minerals 
and food for plants. It must have air and water 
to support plant life. Soil is colored by mineral 
matter and appears as yellow, dull red, gray, 
brown or black according to the amount of iron 
it contains. 

The materials of the mantle rock have been 
sorted into different sized particles and classi¬ 
fied. Names like gravel and sand and mud 
are given to the different materials after they 
have been graded. Gravel is the name for the 
particles that are larger than peas. A single 
piece of gravel is called a pebble. 

Pieces of rock ranging in size from a small 
melon to large rocks often taller than men are 
called boulders. 

Perhaps you have always thought of sand as 
a yellow material something like dirt usually 
found on a shore. The true definition of sand 
is a particle of mantle rock smaller than the 
size of a pea. Sand, also, has been named ac¬ 
cording to its size. It is smaller than gravel 





Soil contains certain minerals and food for plants 


17 














































THE LANDS 


19 


but not as fine as dust. Most gravel is too heavy 
to be carried by the wind, but sand grains travel 
far distances. The sand changes into rounder 
and smoother grains the farther it travels. 

The finest particles of all are called dust. 
Dust that is wet and massed together is called 
mud, silt, or clay. 

Dunes are the mounds formed by wind¬ 
blown sand. When the wind blows sand it 
carries the fine grains close to the ground and 
any obstruction as a shrub, a tree, a stone, or a 
fence will check its velocity. The sand piles 
against the obstruction in drifts. More fine 
grains pile up until great heights are reached. 
The ordinary size of a dune is ten or twelve 
feet because usually the stronger upper winds 
begin to carry the sand away after this height is 
reached. But under certain conditions some 
dunes have reached as high as two or three hun¬ 
dred feet upward. 

Dunes are shaped according to the strength 
and direction of the wind as well as the amount 
of sand and the barrier which lodges the sand. 


What is dust? 


Where do sand 
dunes come 
from? 


What shape are 
they? 


20 


HOW THE WORLD IS CHANGING 


How do they 
travel? 


What is a desert? 


They may be ridges or hills, and often they 
occur in a series. 

As the wind blows constantly upon a dune, 
the sand is transferred from one side to the other 
and the dune is moved. Thus the same sand 
makes the new dune, and it is changed so slowly 
that its transformation is not noticed. But 
dunes are like the tortoise who runs his race 
slowly but surely. They have moved great dis¬ 
tances in this slow steady way. They have 
invaded fertile lands in many instances and the 
people have had to plant trees and vegetation 
on their shifting slopes to help hold them down 
and to keep them from spoiling any more of the 
cultivated countryside. They have even been 
known to bury forests within the period of a 
man’s lifetime. 

A desert is commonly thought of as a stretch 
of land that is practically useless to man because 
it is so dry. It is usually caused by insufficient 
rainfall. It may be in a zone of the world 
where there is little rain, or it may lie to the 
leeward of some mountain range which keeps 


THE LANDS 21 

the rain off. About one-fifth of the lands of 
the world are deserts. We have come to think 
of deserts as all being like the famous Sahara 
where endless stretches of wind-tossed sand 
loom like a yellow sea, where sand storms 
blow with more fury and danger than snow 
blizzards, and sand hills rise like high 
mountains. 

Desert plants also have sharp thorns and 
poisonous juices to protect them from devouring 
animals. The only thing that draws people to 
a desert is the underlying mineral deposit some¬ 
times found in arid sections. On the whole 
deserts are destined to be the lonely places of 
the world. 

The plains bordering the Arctic Ocean and 
the tundras of Eurasia are cold deserts. They 
are barren lands which are covered with snow 
for about two-thirds of the year. 

The cold desert, like the dry desert, is prac¬ 
tically useless to man. Its frozen soil prevents 
agriculture and there is nothing except fishing 
and hunting to draw people to it. Reindeer in 


What is a cold 
desert? 


22 


HOW THE WORLD IS CHANGING 


What is an oasis? 


the cold deserts play the same important role as 
camels do in the sand deserts. 



Reindeer are the steeds of the cold deserts 

An oasis, like a desert, is not usually what it is 
pictured to be in fiction. It is not a beautiful 
little garden in the midst of a sea of sand. It is 
more likely to be large enough to support a town 
and is often a small orchard of date trees rather 
than the two or three trees we have been led to 
expect. One African oasis contains a half-mil¬ 
lion date trees. An oasis is a piece of land in 
the midst of arid lands which is supplied in 
some way by water. It may be from a source 
outside the desert, from a river that starts in a 
well-watered region and runs through the arid 













THE LANDS 


23 


land, or it may be caused by springs or artesian 
wells. If part of the desert reaches an elevation 
high enough to draw moisture from the passing 
winds, this height may become fertile land in 
the midst of a country of barren soil. 

The wind—like the waves—can make ripples 
on the sands. You have seen and felt the hard 
ripply surface of a sandy beach where it was 
shallow enough to touch your feet on the bot¬ 
tom. The surface of dry sand is often rippled in 
the same way by wind blowing over it. The 
ripples are usually very tiny—a fraction of an 
inch or so—and they resemble miniature sand 
dunes, constantly shifting in the direction that 
the wind is blowing, and making patterns on 
the sand. 

Sand is the tool of the wind. It is easy for 
the wind to affect dust and sand, but when it 
blows against solid rock it is powerless. Only 
if it is armed with sand, can it make any im¬ 
pression on rock surface. 

The principle involved is the same one used 
in the etching of glass which is accomplished 


What are 
wind-ripples? 


blow does sand 
carve roc\ ? 


24 


HOW THE WORLD IS CHANGING 


Why is a pebble 
round? 


by a process of blowing sand blasts against the 
glass. The grains of sand make tiny dents in 
the glass. So it is with the wind-blown sand. 
Every grain that touches the rock surface wears 
it in some way. If the rock is of unequal hard¬ 
ness, the sand will dig out the soft portions 
so that it is almost impossible to believe that 
human hands have not been at work sculpturing 
the rock into its new clean-cut form. 

Hard pebbles are smoothed into their round 
flat shape as if they were made of putty instead 
of hard stone. You have picked up smooth flat 
stones near the water or under the water and 
skipped them over the surface of the river or 
lake. You know that these stones have been 
water-worn, but perhaps have never realized 
just what that meant. 

Running water carries the gravel on its bed 
along with it. As the moving stones scrape 
against the rock of the stream’s bed, they are 
worn by the rubbing of rock against rock. The 
points and sharp angles are worn or rubbed 
first and gradually the stone is polished into a 


THE LANDS 


*5 


smooth rounded shape which is usually called 
a pebble. Small pebbles may once have been 
good sized stones, and just as a lemon-drop 
finally disappears after it is sucked for a long 
time, so for a somewhat different reason, a 
pebble may be completely worn away and will 
sometimes disappear altogether. 

A pebble tells where it has been by its shape 
and appearance. The round, smooth pebble we 
have mentioned is water-worn and so we know 
it has been at the bottom of some body of water 
or along a shore where the waves often covered 
it. A faint dimple or dent in the smoothness 
of the surface tells of some collision the pebble 
had on one of its long journeys. Perhaps it was 
washed against a jagged rock. A pebble that 
has traveled with a glacier is not as smooth as 
one that has traveled in the water. It is 
scratched and grooved from its rough journey 
over uneven ground and it has sharp angles 
caused by the jars and blows it has received. 
Pebbles that are buried in the sand are also 
angular rather than smooth, but they have no 


How does a pebble 
tell where it has 
been? 


2 6 


HOW THE WORLD IS CHANGING 


What made the 
mountains? 


deep scratches which characterize the pebbles 
that have been dragged over the ground by a 
glacier. The angular surface is caused by the 
sand drifting over the pebble and scraping 
against it. Pebbles buried in the soil often have 
fern-like patterns marked on them where 
decayed vegetation has touched their surface, 
or they may be covered with a shiny, dark skin 
which forms as a result of the contact with the 
iron oxide in the soil. 

Far back at the beginning of the world there 
occurred the great slow movements of the earth, 
when the continents were squeezed upward by 
the sinking ocean basins. It was then that most 
of the mountain ranges were made. Squeezing 
the continents caused their borders to wrinkle 
up into mountain chains. Some of the ranges 
that were made by the crust of the earth crum¬ 
pling into long, narrow folds are the Alps, the 
Southern Rocky Mountains and the Appalach¬ 
ians. The Alps may be thought of as wrinkled 
earth and if the wrinkles were spread out again 
it would be found that land measuring some 


THE LANDS 


27 


four hundred miles wide had been squeezed to 
a width of less than two hundred miles. 

Another type of mountain—usually standing 
alone rather than in a range, is the volcanic 
mountain. This peak is cone-shaped and often 
very high. It is made of volcanic ash and masses 
of rock hurled forth during an eruption. If the 
volcano erupts frequently, the pile of ash and 
rock grows bigger as time goes on. Fujiyama, 
the Sacred Mountain of Japan, Mount Shasta 
and Mount Rainier are volcanic mountains 
whose cones have reached huge dimensions. 

Other mountain ranges are caused by lava 
beneath the earth which rises toward the surface 
in certain localities, uplifting the rock beds into 
great mounds, sometimes as high as three thou¬ 
sand feet above their surroundings. 

Mountains have not always been peaked. 
The sharp needle-like crags have been carved 
by weather, one of the many sculptors shaping 
the features of the earth. 

Rock is a poor conductor of heat so when it is 
exposed to a dry, sunny atmosphere it becomes 


How are 
mountain pea\s 
formed? 


28 


HOW THE WORLD IS CHANGING 


What is a hill 
a butte? 


very hot on the surface and expands. But the 
inner portion of rock remains cool. Breaking 
and cracking results. In mountain regions, 
especially, the topmost parts of the mountains 
are usually found to be crumbling masses, and 
when there are sharp degrees of temperature 
changes, the loud report of the breaking rocks 
is often heard. In places where it is very hot 
during the day and cool at night, masses of rock 
weighing as much as two hundred pounds have 
been split off. Water will break the rock also. 
The rain fills the pores and cracks in the rock. 
When water freezes, it expands and if the pores 
of the rock are not large enough to hold the ice, 
the rock splits open. This constant shaving 
down and crumbling of the bare and most ex¬ 
posed parts of the mountains has caused the 
forming of crags and peaks. 

Sometimes one section of land is made of 
harder rock than the lands surrounding it. 
Effects of the rain and the weather and some¬ 
times a passing stream will wear down the softer 
rocks of the countryside near and leave the hard 


THE LANDS 


29 


rock elevated. If this hard rock is a small 
section of land it becomes a butte or a hill. If 
it is a larger section, it becomes a plateau. Most 
plateau ranges of any great size, however, were 
caused by a movement of the earth similar to the 
continent-forming movements. Scientists have 
not been able to learn much about plateaus but 
have agreed that they were probably an im¬ 
mense lifting of the lands caused by some verti¬ 
cal force, even more spectacular and greater than 
mountain forming itself. 

As well as the great slow movements of the 
continents and the seas, constant smaller move¬ 
ments are going on. Their effect upon the 
earth’s surface is like the warping of wood. 
They cause slow swellings upward of the land 
—or slow bulgings downward. The sinking of 
a sea border may cause the water to come up 
and cover land that has formerly been above 
sea-level. Uplifted land or a downward move¬ 
ment of the sea may cause the stonework that 
guarded the shoreline in past centuries to stand 
high and dry above the water today. The warp- 


Wky do shore¬ 
lines change? 


3° 


HOW THE WORLD IS CHANGING 


ing of the lands is slow and often very slight— 
from a few feet to a few fathoms a century is a 
spectacular change. Most movements affect the 
land by inches. 

A quicker force than the earth movements 
is the constant beating of the surf against the 
shore. Here is a changing of shore-lines that 
can be seen within the limits of a lifetime. The 
waves and the currents are cutting, smoothing, 
shaping the ever-changing beaches continu¬ 
ously. Water is a skillful sculptor. 

“Waves walk always to a shore”—the coast is 
never free from the dashing of high waves or 
the gentle lapping of the calm undulating 
swells. Off-shore islands are washed away. 
Wave-cut cliffs border the sea. Bays are deep¬ 
ened. Harbors are filled in. The sands with¬ 
draw as the relentless waters push and batter. 
Thus shorelines change and a new rim of the 
sea is formed. 

Waves beating against the base of a cliff 
slowly excavate caves. The wave usually 
washes at an angle slanting upward toward the 


How are sea-caves 
made? 


THE LANDS 


3i 


surface of the land. If the cliff is low, the water 
often forms an opening in the roof of the cave 
and shoots forth in a sparkling, far-flung spray. 



Water slowly excavates caves. If the cliff is low, 
the water often forms an opening in the roof 


As the water digs into the shore, it gradually 
undermines it and the unsupported part falls. 
A steep cliff is left at the water-line. 

Vast ice sheets called glaciers move over parts 
of the earth. They carry along boulders and 
earth and when they have melted they leave 
great piles of this rock in various places. Some 
of it is left off-shore and islands are formed. 
Later, certain of the islands may be connected 
with the land by sand-bars and jutting capes 


What is a 
sea-cliff? 


How are capes 
and off-shore 
islands formed? 










32 


HOW THE WORLD IS CHANGING 


How arc great 
islands formed? 


What is a valley? 


and small peninsulas are formed. Peninsulas 
are also formed by the slow wearing away of the 
coast in one part so that extended arms of land 
are left reaching out into the sea. 

Many large islands like Great Britain are 
thought to be parts of drowned continents that 
have remained above the level of the sea. Other 
islands in the sea are the tops of volcanic cones, 
for there are volcanoes under the sea as well as 
on the land. 

As rain falls on the uneven surface of the 
earth, it disappears in different ways. Part of 
it sinks and forms ground-water, part of it 
evaporates, and some of it runs off the surface, 
finding its way to the sea. Of the water that 
runs off the surface, a greater volume flows 
through the slight hollows than over the level 
ground. As more water flows, the stream in the 
hollow becomes faster and more forceful and it 
digs the hollow deeper. The deepened gully is 
called a ravine. But the process does not stop. 
The streams continue to flow faster and to cut 
the land deeper until the hollow becomes large 


THE LANDS 


33 


enough to be called a valley. A valley is the 
result of many showers running off a depression 
in the land surface and deepening that depres¬ 
sion into a permanent hollow. 

The course of a valley that has grown out of 
a gully is rarely straight because the slope above 
the gully is usually uneven and more water 
comes in from one direction than another. As 
there is more wear on the side with the most 
water, the gully will be turned in that direction. 
It will continue in this direction until some un¬ 
evenness of the land surface allows more water 
to come into it from some other direction. Then 
it will change its course accordingly. 

Besides the main valley caused by the water 
that runs toward the sea, other small valleys 
branch out like limbs from a tree trunk. Wher¬ 
ever the slopes of the gully are marked by a 
slight hollow, water may start running into it 
and another gully is formed. This gully is 
deepened into a ravine and later into a valley. 

The uplifting of two mountain folds may 
leave a deep hollow between. Water may help 


Why is a valley 
croo\ed? 


What is a 
tributary valley? 


34 


HOW THE WORLD IS CHANGING 


In what other 
way can a valley 
be made? 


How does a valley 
change as it grows 
old? 


to deepen the valley, but this type of valley did 
not develop because of water as a gully does. 

An overflowing lake whose water brims over 
at the lowest point in its basin forms a stream 
that flows toward the sea. This stream leading 
out from the lake may drain the lake unless 
surplus water is added continually, and a valley 
is formed when the water has left the stream. 



An old valley has gentle slopes because as it gets 
older the water begins to wear down its sides 


When a valley is young, it is narrow and its 
slopes are steep. But as it gets older the water 
begins to wear down its sides and the slopes 
become gentler and lower so that the valley 
widens. An old valley is wide and flat and its 










THE LANDS 


35 


tributaries, like it, are broad gentle depressions 
rather than steep hollows. 

As long as the valley is supplied with water 
from showers alone, it remains a valley without 
possessing a permanent stream. When the rain 
stops falling, the water in the hollow soon dries 
up and the river that has started to flow dis¬ 
appears. But as soon as the valley is supplied 
with water from other sources than the showers, 
water stays in the hollow and a river is formed. 
The bottom of the valley becomes a river bed. 

A deep and narrow valley is often called a 
gorge if it is small and a canyon if it is large. 
Swift streams with force enough to deepen the 
valley are the main reasons why canyons are 
formed combined with high land slopes made 
of a rocky substance that will not wear away. 
The greatest canyon known is the Grand Can¬ 
yon of the Colorado. It is a mile deep and eight 
to ten miles wide at the top. It is still a young 
valley for its base is very narrow which shows 
that the streams that wash through it have still 
a great deal of cutting down to perform. 


How can a valley 
\eep from turning 
into a river? 


What are gorges 
and canyons? 


What are caverns? 


What is a 
volcano? 


36 HOW THE WORLD IS CHANGING 

The rain that stays beneath the earth is called 
ground water. This ground water dissolves 
parts of the rock and makes it porous. In cer¬ 
tain cases where the rock is made of a material 
like limestone which can be dissolved, instead 
of dissolving parts of the rock, whole sections 
are washed away and caverns are made. Cav¬ 
erns are usually composed of many smaller 
chambers or caves joined by strips of rock. 
Sometimes the roof of the cavern “caves in” and 
there are amazing examples of natural bridges 
that have been formed when a single strip of 
rock remained after the rest of the cavern roof 
had fallen. 

The intense heat within the earth has reduced 
some of the rock to liquid. From time to time 
this molten rock rises to the surface. Part of 
it stays beneath the earth’s crust, but some of it 
rises swiftly and with great violence to the sur¬ 
face where it hurls itself into the air. When 
lava bursts through the crust of the earth, a 
volcano is formed. The hot lava, ash, cinders 
and other materials which are exploded into the 


THE LANDS 


37 


air fall to earth and often form a cone-shaped 
mountain. This mountain usually has an 
opening at the top called a crater. Hot rock 
and gas in small quantities pour continuously 
from the crater and from time to time another 
large eruption may occur where lava in great 
quantities is expelled from within the earth. 
There are about three hundred and fifty active 
volcanoes in the world today. What causes 
lava to burst from the earth in some places and 
not in others has never been agreed upon— 
some geologists think that volcanoes bear some 
relationship to the seas and others believe that 
they are found in places where the earth’s crust 
has undergone changes of various sorts. 

Eruptions of any size bring a great deal of 
danger. The great quantities of steam that 
rise are condensed into water and floods may 
accompany the terrible accident to the earth. 
The gases that issue from the volcano are often 
poisonous or so hot that they destroy life. 
Great pieces of solidified lava are hurled forth. 

The most famous disaster caused by a vol- 


3 » 


HOW THE WORLD IS CHANGING 


What causes an 
earthquake? 


Where is an 
earthquake lively 
to occur? 


cano was the burying of the city of Pompeii in 
79 A.D., when the volcano Vesuvius erupted 
and rained down its cinders and ashes, covering 
the city and all its inhabitants. 

There are constant movements going on be¬ 
neath the surface of the earth. Sometimes a 
portion of the underlying rocks may slip or 
shift their position and a tremor of the earth 
results. If this is violent enough to be noticed 
on the surface of the earth, it is recognized 
as an earthquake. There are undoubtedly 
tremors of the earth that we never feel occurring 
from time to time. 

Like other of the earth’s mysteries, there can 
be no set rules about earthquakes. But geol¬ 
ogists have agreed that certain regions which 
are the scene of changes and movements of the 
earth are more susceptible to earthquakes than 
others. These regions may be near young 
mountains, near the mouths of great rivers 
where sediment is gathering, and land is being 
formed, or in the vicinity of volcanoes where 
temperature is subject to rapid changes. 


THE LANDS 


39 


Earthquakes are less disastrous than they may 
at first seem. Only a few are violent enough 
actually to destroy large numbers of people and 
property. And their effect on the world itself 
is slight. The slumping or shifting of a rock 
beneath the surface is no more than a slight 
movement beneath a coverlet. The surface is 
temporarily disarranged but no permanent 
mark has scarred it. 

An earthquake may fracture surface rock, or 
what is more likely, may open up a crevice that 
was already there but had never been separated 
far enough to make a gap. 

Sometimes a basin-like opening is formed 
during an earthquake, and this is believed to be 
a collapsed cavern of some sort. 

Ground water is sometimes affected, so that 
springs cease to flow after an earthquake. This 
may mean that the earthquake blockaded its 
water supply. The greatest danger is when 
standing water is stirred. Great sea-waves may 
arise, sometimes as high as sixty feet, travelling 
rapidly like walls of water for great distances. 


What are some 
of the effects of 
earthquakes? 


4° 


HOW THE WORLD IS CHANGING 


What causes 
a landslide? 


Can land he 
struct^ by 
lightning? 


These waves sweep over the lands and cause 
loss of life and the submerging of houses and 
lands. 

Coasts often rise or fall during an earth¬ 
quake and the sea-bottom itself may be dis¬ 
turbed so that telegraph cables are broken. 

An earthquake is one means of causing a 
landslide. The shaking of the earth may dis¬ 
lodge masses of rock from cliffs, sending them 
downward. 

But the ordinary cause of a landslide is the 
work of the ground-water that seeps through 
the soil. When the soil becomes full of water 
it begins to slip or slump. If the land happens 
to be on a steep slope, it slides swiftly and in 
large masses. 

A third way in which land falls is when the 
sea waters or rivers have worn away the shore¬ 
line of a cliff and the top of the cliff falls because 
it has no support beneath it. 

There have been rocks struck by lightning as 
well as trees and houses. The rocks were frac¬ 
tured and sometimes moved considerable dis¬ 
tances away. 


THE LANDS 41 

There are evidences of sand having been 
melted together for a short distance when light¬ 
ning struck it, producing a partially fused 
material hardened into a glassy substance. But 
such a thing is so slight it passes unnoticed in a 
world of greater changes. 

Land is being constantly lost—devoured by 
the waters, drowned beneath them, blown away 
by the winds and destroyed by every conceiv¬ 
able force of nature. 

One of the most amazing losses of the land is 
one which is never seen and probably rarely 
thought about. 

The dust in the air often forms mantles a 
hundred feet or more in thickness covering 
large areas of the earth. If all the dust trans¬ 
ported by the winds fell on the lands, a good 
part of the land that is lost would be regained. 
But three-fourths of the earth’s surface is cov¬ 
ered with water and three-fourths of the dust 
that settles falls into the rivers and lakes and 
seas and is lost forever. 


How is land lost? 


Chapter II 


Where did the 

oceans come 
from? 

THE WATERS 

TONG, long ago, when the earth came to rest 
—a battered, wind-blown piece of the sun 
hardened into a great sphere, it hung in space 
gathering in the star-dust—the planet dust—the 
air—and finally the moisture that was in the 
atmosphere about it. The moisture came down 
as rain. 

The surface of the earth was an uneven 
stretch of highlands and lowlands. The rain 
filled the hollows of the lowlands and the oceans 
were made. 

It seems as if something as tremendous as an 
ocean must have been formed in a way more 
complicated and mysterious than the mere spill¬ 
ing of water in a great dish of land, but that is 
all that happened. 

The bottom of the ocean has heights as well 


42 


THE WATERS 


43 


as depths that would be called plateaus and 
valleys if they were on the surface of the land. 
But the broad ranges of highlands are so smooth 
as to seem almost a high plain instead of being 
shaped into hills and peaks as the highlands 
above the earth are. The reason is obvious. 
Beneath the water, the surface is protected from 
the carving of the weather forces. 

There are volcanoes on the bottom of the 
ocean—some of which rise so high that their 
tops appear above the surface of the water and 
form islands. 

At the bottom of any body of water, deep or 
shallow, there are certain deposits of sediment. 
The different materials that make up these de¬ 
posits are interesting to discover. Many of them 
have traveled great distances. 

Near the shores the deposits are mostly sand 
and gravel and mud washed from the lands. 
This same type of material persists as far out as 
the too fathom mark. But beyond that, in the 
deep sea beds, more varied deposits form. Here 
are found various matters of organic or chemical 


What does the 
ocean bottom 
look li\e? 


What corresponds 
to mantle rock 
under the seas? 


44 


HOW THE WORLD IS CHANGING 


What are the 
colored muds? 


What are the 
oozes? 


What accidental 
deposits have been 
found? 


origin called oozes as well as the colored muds. 

It sounds like a fairy story to say that blue, 
red and green mud are found at the bottom of 
the sea. To explain how these muds became 
colored it is necessary to understand chemistry, 
but, to say it simply, their color is dependent 
upon the changes they have passed through 
since they were deposited beneath the waters. 

The oozes are largely made up of shells and 
skeletons of creatures of the sea that live near 
the surface and fragments of sea plants. When 
these marine animals die, they sink to the 
bottom with their shells and form a part of the 
deposit there. 

Sometimes in the deep sea beds land mate¬ 
rials are found that must have been brought 
there by some strange chance. Boulders have 
been discovered. One explanation is that they 
were caught in the roots of floating trees and so 
carried far out beyond the shallow deposit 
region where they belong. Another explana¬ 
tion is that giant icebergs, carrying rocks and 
other land materials embedded in their frozen 


THE WATERS 


45 


bodies, floated seaward where they gradually 
melted and released their strange cargoes. 

Volcanic glass and ash have also been found 
and certain magnetic grains which are thought 
to be part of fallen meteors. 



A strange, dim, green world of plants with ex¬ 
traordinary fish swimming about 


The oceans cover three-fourths of the surface 
of the earth. If the earth did not have high¬ 
lands, it would be completely covered by water, 
measuring about two miles deep everywhere 
on its surface. 


What are the 
measurements 
the oceans? 



4 6 


HOW THE WORLD IS CHANGING 


What makes the 
ocean salty? 


The surface of all the oceans has been esti¬ 
mated to be about 143,259,300 square miles. 

The deepest point thus far known in the 
oceans is 31,614 feet below the surface of the 
Pacific at a spot near the Ladrone Islands. 
This is an exceptional depth and is what is 
meant when people refer to the “deeps” of the 
sea. The greatest average depth ranges from 
12,000 to 18,000 feet, though a large area is as 
shallow as 6,000 feet. 

Rivers are constantly emptying their waters 
into the sea. With this inflow comes quanti¬ 
ties of mineral deposits. More than three- 
fourths of the dissolved mineral matter in the 
ocean waters is common salt. 

There are other important deposits as well. 
Calcium carbonate is one of them, but it is con¬ 
stantly used by sea creatures to make their shells 
so it is used up nearly as fast as it comes. There 
is little use for salt, however, and that is one of 
the reasons there is so much salt in the seas— 
it has stayed there, adding to its quantity for 
millions of years. 


THE WATERS 


47 


In the slow movements of the earth we have 
seen that there are warpings of its surface so that 
the borders of land and sea are sometimes 
lowered. Downward movements of the land 
have often been the cause of great shallow seas, 
where the ocean has flooded the lowered con¬ 
tinent over a great area. Such a submerged 
continent is called an epicontinental sea. The 
North Sea in Europe is an example of a shallow 
sea and Hudson Bay in North America is 
another. 

The pictures we have seen of a strange dim 
green world of plants with extraordinary fish 
swimming about in it are all portrayals of 
shallow waters. The ocean deeps have no life 
except near the surface of the water. But the 
fantastic scenery of under-sea countries does 
exist, where sea-weed grows to lengths that 
would stretch out taller than the tallest trees 
and is often six inches in diameter. Many sea 
plants float, giving them an eerie effect of being 
alive. Contrarily, the animal life is often fixed 
and barnacles and polyps may live their entire 


What is a shallow 
sea? 


What is the life of 
the ocean world 
li^e? 


What influences 
affect the oceans? 


48 HOW THE WORLD IS CHANGING 

lives on the sea bottoms half buried in the 
soft mud. 

The temperature of the water affects life in 
the water much as it does on the land. Just as 
certain animals are found only in cold climates 
on earth, so seals are only found in cold waters. 
Just as tropical creatures flourish only in the 
warm climates, so coral reefs are made in warm 
waters by the polyps who like water that is 
shallow, clear and warm. 

The greater the depth of the ocean, the colder 
it is. The average temperature of the ocean is 
probably about 39 degrees F., but in shallow 
waters it may be as high as 60 degrees F., and 
the deeps may be as low as 35 degrees F. 

Just as the countenance of the land is changed 
by rainfall and temperature, by wind, by ice, and 
by the internal movements of the earth, so the 
ocean is affected by outside conditions. 

When the wind blows over the seas it creates 
waves. The waters may rise as high as forty 
feet in a storm. If the air is still, the water may 
become glassy and very calm. The calm may 


THE WATERS 


49 


be as terrifying to seamen as the storm. Much 
has been written of the voyages that men have 
taken since the far of? days when the wind was 
necessary to sailing vessels. 

Larger movements than waves are constant 
circulators of the waters which are called ocean 
currents. Ocean currents are started chiefly by 
the winds and directed by them as well as by 
the position of lands, the rotation of the earth 
and the depth of the waters. 

The Gulf Stream is one of the most famous 
of the ocean currents. Often, coming out of 
stormy, wintry seas into the Gulf Stream, the 
voyager will be able to go without his coat on 
deck for two or three days. When the Gulf 
Stream is left behind, he must put on his 
woolens and shiver beneath his steamer rug 
again. 

The sun and the moon attract the earth some¬ 
what as a magnet attracts steel. They pull the 
earth toward them slightly and the waters are 
disturbed and the movements that result are 
called tides. 


5° 


HOW THE WORLD IS CHANGING 


How is a bay 
formed? 


How are la\es 
made? 


Earthquakes and the eruption of volcanoes 
may affect the bottom of the sea much in the 
same way that land surface is disturbed. Proof 
of this is shown by the volcanic ash and cinders 
found on the sea bottom and by the breaking of 
telegraph cables when an earthquake lowers the 
sea bottom or obstructs it by an upheaval. 

When the sea rises and covers the surface of 
the land, new coast-lines are made. The water 
follows the contours of the land, and naturally 
more water flows into the hollows of the land 
than over the level surfaces. Often the lower 
parts of valleys are filled with water and bays 
are formed. There are other ways of forming 
bays. Small inlets may be made by the water 
wearing away the land. Coast-lines change 
and the waters invade the level areas between 
the uplifted lands. The majority of bays, how¬ 
ever, may be thought of as drowned valleys 
caused by the flooding of the waters. 

A lake resembles a miniature ocean. It, too, 
fills a basin of earth. Many lake basins were 
dug by glacier movements either in bed-rock 



Old Faithful in Yellowstone Par\ erupts regularly every hour 
or so 


51 











THE WATERS 


53 


or in the drift that the ice sheet carried with it. 
Other lakes are made by rivers. When a river 
floods over, its banks are built up by deposits of 
earth and sometimes dams are formed. The 
flood on the other side of the dam becomes a 
pond, which in time may turn into a lake. 

There are a few lakes in the world that are 
salty like die ocean. Certain of the salt lakes 
were probably parts of the ocean at one time 
and through some change of the earth’s surface 
became separated from the seas by land. Other 
salt lakes were once fresh water lakes. They 
are situated in a dry climate. If it is dry enough 
so that the water in the lake evaporates faster 
than fresh water is added, the salt that the fresh 
waters bring in does not evaporate and becomes 
more noticeable because there is less water in 
the lake to dilute it. 

When a lake is drying up, it is called a marsh. 
When a marsh dries up, the lake becomes 
extinct. 

The rain that sinks beneath the surface of the 
earth and stays there is called ground water. 


What are salt 
la\es? 


What is a marsh? 


What is ground 
ivater? 


54 


HOW THE WORLD IS CHANGING 


What happens to 
ground water? 


What is a geyser? 


What is a river? 


The soil is loose and absorbs the water easily so 
that it seeps through to the rock beneath where 
it sometimes sinks into cracks that are very deep 
in the earth. 

Some ground water evaporates, some is 
sucked up by plants, some forms wells or 
springs, and some returns to large bodies of 
water like rivers and lakes. 

A geyser is a hot spring which erupts at 
intervals as a volcano does. There is some mys¬ 
terious connection between geysers and vol¬ 
canoes which has never been fully explained. 
This is known because geysers are found only 
in volcanic regions. It is believed that the 
water of a geyser is heated by lava under the 
earth. 

Some geysers erupt at periods of years apart, 
and others, like old Faithful, spout their waters 
every hour or so. 

When valleys are made and are watered only 
by rain they remain valleys, but if sufficient 
ground water feeds them or water from some 
other source is given them, a permanent stream 


THE WATERS 


55 


is formed in the valley bed, which is called a 
river. 

An old stream is one which moves along 
sluggishly and instead of cutting its channel 
deeper, widens it and floods over the banks. 

A waterfall can be made in a river where the How are water- 
bed is composed of soft and hard rock. The ^ alls f ormed? 



The water jails over the high roc\s 


soft rock is cut lower by the water and the hard 
rock remains high. The water falls over the 
high rock. 

If the course of a river is directed toward a 
cliff, the stream continues to flow, dropping 
over the cliff in a waterfall. 







56 


HOW THE WORLD IS CHANGING 


What is a delta? 


What accidents 
may happen to 
rivers? 


What is a snow 
field? 


When a stream flows into a larger body of 
water as a sea or a lake, its current is stopped. It 
ceases to be a stream and merges with the greater 
body of water. It drops its load of earth and 
bed-rock materials that it has washed along 
with it at the place where it enters the larger 
body of water to become a part of it. If the 
material that it drops is not later removed by 
the waves a delta is formed. A delta is usually 
shaped like a fan and like the Greek letter a 
which is called delta and gave the river deposits 
their name. 

Besides having their water stolen by other 
streams, rivers may have their flow endangered 
in other ways. If the lower end of a valley sinks 
below sea-level, the sea floods the valley and 
forms a bay, thus drowning the river that was 
formerly there. 

In certain parts of the world, usually moun¬ 
tainous sections or the arctic regions, where a 
low temperature exists all year long, snow never 
melts entirely away. It lies in great stretches 
of white waste. It does not remain pure snow, 


THE WATERS 


57 


however, for long. The light flakes become 
coarser and harder until layers of ice are formed. 

The ice piles up—season after season. Some¬ 
times a layer of earth comes between the ice 
of one year’s winter and that of the next. 

After a while the great ice field begins to move 
slowly. When it begins to move, it is no longer 
a snow field. It has become a glacier. 

A glacier may range from a fraction of a mile What is a glacia¬ 
te many miles in length. They are usually lt ^ e? 
longer than they are wide and hundreds of feet 
thick. In the Alps they often range from five 
to ten miles in length. Glaciers, like sand 
dunes, move too slowly to be seen by the human 
eye. They are measured by various tests and 
have been found as a rule to move three or four 
inches a day. Certain glaciers in Greenland and 
Alaska move much more rapidly—the Muir 
glacier in Alaska moves seven feet a day and 
some of the Greenland glaciers as much as 50 
or 60 feet a day. The record is 100 feet in a 
single day. 

A crevasse is a break or fracture in the mov- 


58 


HOW THE WORLD IS CHANGING 


What is a 
crevasse? 


How does a 
glacier affect the 
land surface? 


What is an 
iceberg? 


ing ice sheet, often very deep and wide. A 
glacier sometimes cracks if the ground it moves 
over reaches a higher level. 

A glacier moves over the land like a giant 
plough, uprooting rocks and earth and even 
trees in its path. When it moves through 
valleys it often widens the bottom of them and 
smooths their slopes so that the valley that was 
V-shaped before becomes U-shaped after a 
glacier has gone through it. 

As a glacier usually melts before it reaches the 
sea, it drops its load on the lands more often 
than in the waters. Valleys may be filled with 
glacial deposits and certain soils are glacial 
drifts. If the glacier should reach the sea, 
islands may be made off-shore by the dumping 
of land materials onto a relatively shallow 
bottom, and the glaciers become another means 
of wearing away the continents. 

When glaciers reach the sea, certain parts of 
them break up and float away and these masses 
are called icebergs. They float like mysterious 
boats over the waters, sometimes carrying 



Icebergs float li\e mysterious boats over the ivater 


59 


















































THE WATERS 


61 


strange cargoes of boulders and earth far dis¬ 
tances from the lands. 

In the days when the world was filled with 
fantastic forms of giant creatures and when 
man had not yet made his appearance or was 
just coming into existence, the climates of the 
earth passed through great changes and tem¬ 
peratures were reduced. Great sheets of ice 
moved slowly over large areas of the lands, 
blotting out life. Then the climates grew 
warmer and the ice melted. Life began to grow 
once more in the areas once ice-covered. Again 
the glaciers were formed. The animals fled 
southward or were killed. Indeed it is believed 
that the great ice age was the cause of many 
types of strange mammoth creatures vanishing, 
never to return. 

Ice plays a dramatic part in the history of life, 
whether it is this ancient ice that destroyed life 
so mysteriously, or whether it imperils life in 
our own time. The Titanic struck an iceberg 
and what was thought to be an unsinkable ship 
was lost. Every year there are stories of Alpine 


What were the 
ancient glaciers 
like? 


62 


HOW THE WORLD IS CHANGING 


What is the 
importance of 
water? 


climbers who have fallen into a crevasse. Often 
years later, as the glacier moves its slow and 
steady course, the frozen body of some lost 
climber is brought down into a valley, and the 
crevasse gives up its victim. 

Water takes various forms as it appears on 
the surface of the earth. In each form, it is 
of infinite value to humanity and to the lands. 
It is a means of transportation. It irrigates the 
soil. Its power creates electricity for man. 
When it contains minerals it is health-giving 
—and in any form that is pure, it is necessary 
to our existence. 

There is ever something awe-inspiring and 
dramatic about it. It carries danger in its wake. 
Flood and shipwreck and tidal wave have all 
played their part in the exciting fiction of its 
history. Men of the sea must be stern of heart. 

But it is invaluable. Its dangers are prob¬ 
ably less than those on the lands but because a 
tragedy at sea stands out alone and isolated it 
looms before us. 


Chapter III 


THE INSIDE OF THE EARTH 

J UST as we cut an orange in half and find 
sections, and an apple in half and find a 
core, so if we could cut the earth in half we 
would find that the world we live on seems to 
be made up of layers. These layers are of many 
different kinds and colors and substances. They 
are like the layers of Black Ball candy that you 
bought when you were small. The outer layer 
was black—when you licked that off the ball 
became pink. When the pink layer melted, the 
ball was white and finally in the very center 
hidden beneath all the layers was a hard little 
caraway seed. The earth has an outside rim 
that we can see with our own eyes. It is called 
mantle rock. This layer measures from a few 
feet to several hundred feet deep and is made of 
earth and broken rock. Next appears a great 


What would the 
earth loo\ like 
if it were cut 
in half? 


63 


6 4 


HOW THE WORLD IS CHANGING 


Is the inside of 
the earth hot? 


zone of solid rock composed of many different 
layers, built in sections like the floors of an 
apartment building and extending some fifty 
miles downward. And finally—at the very 
center of the earth about 4,000 miles beneath 
us is a core that is probably of a metallic sub¬ 
stance. This has never been seen, so we can 
only imagine it and believe it is there because 
the scientists have reached that conclusion after 
years of study and experiment. 

We know that the temperature of the interior 
of the earth must be very hot. When the waters 
of a geyser shoot into the air, they are boiling 
and steaming, and if a volcano erupts, the lava 
is a hot stream of melted rock. One cause of 
this heat is probably the intense pressure of the 
layers of rock, one on top of another. The heat 
that arises is kept alive because the outer layers 
of rock are like a blanket protecting the hot 
center from the cool atmosphere without. One 
scientist believes that the temperature at the 
center of the earth is about 36,000 degrees F., 
but there are contradictory opinions. 


THE INSIDE OF THE EARTH 


65 


The rocks of the earth arc divided into two 
great classes, according to the way in which they 
were formed. A third classification is given to 
a rock that combines the characteristics of the 
first two. One type is called crystalline or ig¬ 
neous rock. It is formed by the hardening of a 
hot liquid substance inside the eardi from pres¬ 
sure under conditions of high temperature. It 
is really hardened lava in its rock state. The 
second class includes all the sedimentary rock 
and is called stratified rock. These rocks are 
formed by deposits, blown by the wind or car¬ 
ried by moving glaciers or running streams. 
Often sedimentary rocks are made of the broken 
and crumbled crystalline rocks that have been 
cemented together with other materials of the 
earth and hardened. Stratified rock occurs in 
layers, usually relatively thin because they are 
soon covered up with a new layer of sediment. 
The older a layer of rock is, the deeper down 
it lies, for it has had many years to be covered 
up by new layers. Metamorphic rocks are 
formed from both igneous and sedimentary 


What arc the 
principal classifi¬ 
cations of roc\s? 


66 


HOW THE WORLD IS CHANGING 


What are the jour 
great series of 
sedimentary 
roc\s? 


rocks, if the original deposit has been greatly 
changed by subsequent pressure, heat or chemi¬ 
cal agencies. 

Beneath the earth, then, are layers of rock. 
These layers are called strata . The four greatest 
series of sedimentary rocks were probably once 
beds of the oceans. They represent four great 
periods in the history of the earth. From the 
fossils embedded in them, men can tell what 
kinds of animals lived in each period and they 
can picture fairly accurately what the world 
was like then. The oldest layer of the four is 
called the Proterozoic . It means earlier life. 
It contains very few fossil records because life 
at that very ancient period was too tiny to leave 
any impression or to be preserved. The next 
layer is called Paleozoic which means ancient 
life. Many records are already found in this 
strata. In the Mesozoic , a period of middle life, 
the sedimentary rocks contain still more fossils, 
and the Cenozoic, a strata of recent life, is a 
fairly complete chapter of knowledge and his¬ 
tory of organic life. The shell of the earth has 


THE INSIDE OF THE EARTH 


67 


other layers of rock, but these four series are 
principally sedimentary in origin and are of the 
most importance because only sedimentary 
rocks contain fossils, or metamorphic rocks 
formed from sedimentary. 

Igneous rocks are formed from a hot liquid why are there no 
rock which either hardens before it reaches the f osst ^ tn igneous 
crust of the earth or as soon as it has reached it. 

Therefore fossils are never found embedded in 
them. Fossils are the remains of living plants 
or animals. They are caused by the preserva¬ 
tion in rock of dead creatures or vegetation. To 
be preserved, the relics must be covered over 
with layers of sediment and protected from de¬ 
cay. Igneous rock hardens before any relic has 
a chance to be preserved or hardens beneath the 
surface of the earth where animal life does not 
exist. 

The oldest rocks on earth are of igneous 
formation and form a foundation series called 
the Archean era. They are known to be very 
old because they lie beneath the sedimentary 
rocks. 


What is decayed 
roc\? 


What causes the 
coloring in rocks? 


68 HOW THE WORLD IS CHANGING 

The outside crust of the earth is made of 
decayed rock. The hardest rock will decay if 
it is exposed to the harsh conditions of the 
weather. It may take years of wearing down 
to finally reduce the rocky substance to soil but 
if it is exposed to the force of air and water 
it is almost certain to lose its original form. 
This outside layer of decayed rock later becomes 
one of the inside layers of rock, after it has 
been covered up and has hardened into a new 
rock formation. Water is the greatest enemy 
of rock. It penetrates into the cracks and open¬ 
ings of the rock and when it freezes, it expands 
and splits open the boulder. Trees and growing 
plants are another enemy. Beneath the surface 
of the earth their roots push out in all directions. 
If the roots touch a rocky surface, the force of 
the pressure is often enough to break the rock 
and start it crumbling on its way to decay. 

The color in rocks is due to the presence of 
minerals. Iron is one of the most ordinary 
minerals found in both igneous and sedimen¬ 
tary rock. Iron will color a rock dark green, 


THE INSIDE OF THE EARTH 


69 


dark brown or black. In sedimentary rocks all 
red-brown colors are caused by iron but grays 
and blacks are usually the result of the presence 
of carbon. The lovely amethyst shade found in 
certain crystalline rock is due to a small amount 
of maganese oxide in the quartz. The green 
of other semi-precious jewels is probably a color 
created by chromic oxide. 

Sedimentary rocks usually follow a certain 
color chart. The shadings of the red-brown 
tones caused by the presence of iron range from 
pink, red, dark red, to red brown. Another 
range of yellow brown tones indicates that 
limonite is in the rock and the rock is colored 
pale yellow, buff, or yellow brown. The range 
of whitish grays to black indicate carbon is 
present to the degree it has discolored the rock. 

The Dolomites, a mountain region of the 
southern Alps, contain some of the most star- 
ding streaks of color in the various peaks imag¬ 
inable. They are named after the sedimentary 
rock called dolomite which is formed from pure 
limestone partially mixed with magnesium. 


7 ° 


HOW THE WORLD IS CHANGING 


How are crystal¬ 
line roc\$ formed? 


Deep down near the center of the earth is a 
layer of rock that is so hot it is in a liquid state. 
If the pressure of the earth bears down upon 
this liquid, it hardens and becomes a part of the 
metal core of the earth. But if for some reason 
it fails to harden, it often pushes its way toward 
the earth’s surface. Sometimes it bursts forth 
and a volcano is formed, but often it nears the 
crust of the earth and is stopped in some way. 
There it usually cools and gradually hardens. 

When this liquid or molten mass of rock 
cools slowly and becomes solid, the minerals in 
it form crystals. Crystals are particles in the 
rock that always have the same part to play in 
the making of rock of this kind. They are the 
mineral materials of the rock that have become 
separate bodies under the power of changing 
temperature. If the hot rock cools slowly, the 
crystals are large. It it cools quickly, the crystals 
are so small they cannot be seen and are some¬ 
times not formed at all. Rock formed so quickly 
that the mineral material did not have time to 
turn into crystals is glass. 


THE INSIDE OF THE EARTH 


7i 


This question sounds like a riddle with a 
trick answer, but its answer is true and scien¬ 
tific and is found in the story of crystalline 



Crystals formed from the minerals in crystalline 
roel( 


rocks. The granite that is used for so many 
fine buildings in the world is a liquid rock 


Why is a granite 
building li\e a 
precious jewel? 


HOW THE WORLD IS CHANGING 


72 


Why are some 
crystals more 
precious than 
others? 


which cooled and grew solid very, very slowly. 
The crystals in granite are large and firmly 
welded together so that the rock is very strong. 
Granite, then, was made by a stream of liquid 
rock gushing forth from the hot centers of the 
earth and cooling into a solid mass before it 
reached the surface of the earth. Perhaps the 
block of granite was never discovered until 
many layers of rock covering it, had worn away. 

Precious stones are nearly always some form 
of the crystals that have formed from the 
minerals in crystalline rock. When you see 
shining, sparkling particles in a piece of granite, 
you may know that they are some distant rela¬ 
tive of valuable precious stones. 

The crystals in rock are formed under dif¬ 
ferent conditions—some are made slowly, others 
quickly. Some have different combinations of 
mineral materials than others. Some are 
harder in substance. All these things go into 
the history of the creation of precious jewels. 

The stones that are purest, not marred by 
cracks or clouded by other materials, colored 


THE INSIDE OF THE EARTH 


73 


most beautifully, hardest, and most sparkling 
become the most valuable. 

Stones like diamonds, rubies, sapphires, and 
emeralds are more valuable than the amethyst, 
rock crystal, or topaz because they possess qual¬ 
ities of hardness, brilliancy, and color that are 
uncommon and are only found in certain places 
in the world. 

Jewels are colored in two different ways. 
They may contain a colored substance and take 
on that color as the amethyst does. This is the 
same principle as the waters of the sea being 
colored by coral beds. Or they may be color¬ 
less and reflect rays of light on their irregular 
surface in miniature rainbows as a diamond or 
an opal does. 

For hundreds of years, the imagination of 
man has been captured by the beauty and value 
of precious gems. Primitive people have had 
superstitions about them. Jewels were supposed 
to be able to cure diseases. They were used for 
charms. They were lucky or unlucky. To this 
day plays are written of the disaster that fob 


What colors 

precious 

stones? 


What is the 
romance of 
a gem? 


74 


HOW THE WORLD IS CHANGING 


lows the Cat’s Eye, and birthday stones are a 
common tradition. 

Not only in mystery and adventure stories 
but in history itself, precious gems have had 
their own careers, borne names that are recog¬ 
nized years after their discovery, and lived lives 
as dramatic as those of human beings. There 
is the mysterious tale of the “Great Mogul,” 
once owned by Emperors of Hindustan, which 
ends in the vanishing of the jewel. Where was 
it lost? Where is it hidden? The two largest 
diamonds in the world are the “Excelsior” and 
the “Cullinan.” What will be their story—will 
they too disappear some day? The Cullinan, 
found in 1905, weighed when it was found 
about one and a half pounds and measured 
four and a half by two and a quarter inches. It 
was cut into nine large stones, two of which are 
the largest cut diamonds in the world, and 
about a hundred smaller ones. It belongs to 
the British Crown. 

The romance of the creation of jewels is a 
fascinating tale. The crystals in diamonds are 


THE INSIDE OF THE EARTH 


75 


made principally of a substance called carbon. 
By some curious twist of fate, ordinary coal— 
made from a different process entirely—has 
for its principal material this same carbon. 
This coincidence is like two brothers who are 
equipped with the same ancestry, but brought 
up in two different places under different con¬ 
ditions, they become two different types of men. 
Perhaps one is a poet, and the other is a plumber. 
Thus the diamond, prince of the materials of 
the earth, is closely related to a lump of coal. 

Stratified rocks are formed when all kinds 
of loose materials on the surface of the earth— 
clay, sands, gravels, volcanic ashes or cinders, 
become hardened by pressure or cemented by 
water and hardened when the water dried out. 

A material like sand is formed from particles 
of crumbled granite, worn by weather and other 
forces of nature into a powdery form. Gradu¬ 
ally the loose bed of sand becomes sandstone, 
as soft deposits of fragments of shells may be¬ 
come limestone and hardened clay may turn 
into slabs of slate or shale. 


How were 
stratified ro 
made? 


76 HOW THE WORLD IS CHANGING 


What is 
house? 


In the arid regions of western North America, 
especially in the regions of the southwest near 
adobe the Mexican lands, houses are often built of a 
fine-grained material called adobe . This is a 
sun-baked clay made into bricks. It has the 
characteristic rock colorings: yellowish, yellow- 
brown, gray-brown, or chocolate brown. 

The origin of this yellowish dust is the rock 
of the mountains and higher slopes of the hills 
in neighboring regions. Here the decayed rock 
lies in crumbling surface soil. It is carried 
down to the lower plains by rain wash and the 
wind. The surface of the earth is constandy 
moving downward. Gravity is one of the 
causes of this downward movement. All things 
fall down. The earth that rests on a hill top 
has a natural tendency, then, to fall down too. 
Water runs down also. The water seeking a 
lower level carries with it the light rock dust. 
Down in the valleys people foimd that the rock 
dust mixed with water and hardened made a 
perfect building material and so the adobe 
house was originated. 



In Mexico, houses are often built of a fine-grained 
material called adobe 


77 




























THE INSIDE OF THE EARTH 


79 


The hard granite that is a crystalline rock 
and the much softer sandstone, a stratified or 
sedimentary rock, are near relations. Sandstone 
is made principally of the quartz that was 
broken up when a slab of granite was exposed 
to the air. The color of sandstone may be very 
different from granite—it may even be brick 
red. This is caused by the material which 
cements the pieces of quartz together. Mud or 
lime may cement the particles of quartz, and 
the iron contained in them is often the coloring 
agent that turns the substance red. 

Gold and silver are only two of some 1500 
kinds of minerals found in the earth. These 
minerals may be fuels like coal or petroleum; 
metals like gold and silver; or precious stones 
like diamond and sapphire. The minerals 
themselves were caused by heat within the earth, 
but the forms in which they appear are the 
result of all the countless changes that they 
have gone through. Thus diamond and coal 
may be composed of the same mineral matter 
but are quite different in appearance because 


What two build¬ 
ing materials 
are closely 
related? 


What is gold 
and silver? 


8 o 


HOW THE WORLD IS CHANGING 


What is coal? 


the mineral went through a different process in 
formation. 

Most of the minerals that become metals are 
found in the veins of rock. A vein is a crack 
or crevice of the rock bed. One of the principal 
ways of filling a rock vein with a mineral de¬ 
posit is by the work of ground water. This 
underground water seeps through the earth, 
washing the minerals from the lighter soils. 
These minerals are deposited in the cracks and 
crevices of the layers of rock beneath the sur¬ 
face. Changes caused by heat and pressure and 
water take place and the mineral deposits be¬ 
come veins of gold, silver, lead, zinc, copper 
and other materials. 

Coal occurs in layers like stratified rock. 
It is not made up of particles of other rock as 
sandstone is. It is an organic rock, formed from 
the compressed and changed remains of vege¬ 
table life which once grew where the coal bed is. 

The great coal beds of the world were formed 
millions of years ago. The plants that became 
coal were giant ferns and fern-trees that prob- 


THE INSIDE OF THE EARTH 


ably grew in swamps near the sea. The trunks 
of trees and vegetable matter were covered with 
other sediments like sandstone which pressed 
down upon them. The hidden layer of plants 
became coal. Coal contains a great deal of 



The hidden layers of plants became coal 


carbon, and it is this very element that in a 
different form may become diamond instead of 
a humble fuel. 

Peat is another form of organic sediment. 
Coal has more carbon in it than peat and is 
harder. Peat is made almost entirely of the 
vegetable matter as it grew in the bog. 

Coal, like petrified wood, often shows the 







82 


HOW THE WORLD IS CHANGING 


What are the 
different {inds of 
coal? 


shadings and patterns of the plants from which 
it was made. 

Besides the ordinary Bituminous and Anthra¬ 
cite coal, there are many other specialized kinds. 
Bituminous coal is a soft coal, gray-black to 
velvet-black in color. It burns with a yellow 
flame. It is the chief coal of the world and 
there are still enormous quantities of bituminous 
coal in the world. They will not be exhausted 
for a thousand or more years to come. 

Anthracite coal is a hard coal, iron-black to 
velvet-black in color. It burns with a pale blue 
flame and requires a large amount of heat to 
start burning. There is no smoke or odor in 
burning so that people are urged to use it in 
order to keep their city air free from smoke. 
It is much less common than Bituminous and 
so it is more expensive. Most households use it 
while factories are forced to burn soft coals 
which are not so high priced. 

One of the specialized coals is Cannel coal. 
a form of soft coal. It is a dull black in color. 
]ct> a soft coal similar to Cannel coal, has a high 



The oil fields are immensely valuable to man 


83 



























































THE INSIDE OF THE EARTH 


85 


luster and is a more intense black color. The 
well-known jet beads that you can buy in the 
stores are made of this variety of coal. Coal 
is used for the making of gas and coke. 

The petroleum or oil fields in our country 
are immensely valuable to man. Petroleum is 
a mineral oil commonly believed by scientists to 
be an outgrowth of decayed animal and vege¬ 
table material. 

Iron-bearing springs abound throughout the 
earth. If an iron spring is exposed to the air, a 
solution of the iron in the water may form under 
the various changes of temperature and condi¬ 
tions. This usually occurs in a marshy land 
and the deposits are known as “bog-ore.” Iron 
ore may also form around shallow lakes or at 
the bottom of peat bogs or in connection with 
coal formations. 

A chalk cliff is a specialized form of rock, 
white-colored and made of a substance almost 
entirely composed of lime. It is a mass of 
broken skeletons of sea forms and the shells of 
very tiny sea creatures. Chalk is an organic 


What ts 
petroleum? 


How are iron 

ore-beds 

formed? 


What is chali{? 


86 


HOW THE WORLD IS CHANGING 


Where does 
come from? 


rock too, but instead of being made of plant 
organism it is composed of animals’ remains. 
The chalk cliffs were probably begun thousands 
of years ago. When sea creatures died, their 
shells sank slowly to the sea-floor. Again and 
again throughout the years this deposit of shell 
and bone substance containing lime was de¬ 
posited. Finally layers of lime were formed. 
Perhaps the ancient sea dried up—or the land 
may have risen, until finally this strange rock, 
that was made of sea-creatures which had been 
hardened under the pressure of water and de¬ 
posits, emerged as a beautiful white cliff. 
salt Nearly all the salt beds in the world are be¬ 
lieved to be the remains of ancient salt waters 
that have dried up. When the water evapo¬ 
rated, the salt was left. These deposits were 
often very thick so that the salt has to be mined 
from beneath the ground very much as coal is 
mined. A large salt mine in the United States 
lies a fifth of a mile below the surface and air 
is pumped down hourly to protect the life and 
health of the workmen. At Stassfurt, Prussia, 


THE EFFECT OF THE EARTH ON MAN 87 


there are salt beds 300 to 500 feet thick. A 
description of a salt mine tells of brilliant lights 
gleaming against snowy walls, and of work¬ 
men’s huts carved out of salt like a sugar house 
in a Grimm’s Fairy Tale. 

Salt Lake in the United States is said to con¬ 
tain about 400,000,000 tons of common salt. 
If in some future day the lake should happen 
to dry up, great white fields of salt would be 
left. This is exactly what has happened in the 
past where other lakes have dried to cause the 
salt beds that exist in various parts of the world 
today. 

The inside of the earth is one of the profound 
mysteries of the world. It contains the secrets 
of the past. The rocks that are laid down in 
layers have imprisoned the remains of life from 
other worlds and times and a marvelous record 
of all that is ancient and gone can be uncovered 
at man’s will. Hardened with the rocks or em¬ 
bedded in them, are the skeletons and remains 
of plants and animals. They are called fossils. 
Fossils tell us a story of strange creatures that 


What is the 
greatest mystery 
of the earth? 


88 


HOW THE WORLD IS CHANGING 


walked the earth in bygone eras of geologic 
time. 

The inside of the earth is hot and filled with 
strange brews like a witch’s cauldron. Melted 



Hot steam may burst forth 


rock may rise in streams of fiery liquid and 
create great damage. Rocks may shift and fall 
and the earth cracks open. Hot steam may 
burst forth. 

The inside of the earth is a treasure mine. 
















THE EFFECT OF THE EARTH ON MAN 89 

Gold and silver and precious jewels are hidden 
there. Coal and iron that we need for comfort 
and progress and gravel pits and sandstone 
quarries that yield us building materials—all 
these are a part of the dark depths that we know 
so little about. 


Chapter IV 


Can man change 
the earth? 


THE EFFECT OF THE EARTH ON MAN 

W E HAVE seen how the earth is con¬ 
stantly changed through the forces of 
weather, of pressure, of inward heat, and by 
the great slow movements that have continued 
for centuries. Some of these forces man can 
control. A drainage system may change desert 
wastelands into property that is fertile enough 
to be of some use to its inhabitants. Swamp¬ 
lands may be reclaimed. River floods can be 
held in check. Streams are deepened and 
widened by the hand of man. Certain things, 
then, can be done to chain the earth to man’s 
convenience. 

But for the most part, man is the helpless 
slave of the earth and its greater movements. 
He is powerless against a mountain range. He 
is unable to drain the waters of a vast ocean. 


90 


THE EFFECT OF THE EARTH ON MAN 91 


He cannot check a glacier or a volcano or an 
earthquake. And so his life is built around the 
conditions of the place he lives in. He must 
change with each generation—or perhaps with 
every year—to meet a changing world. 

Three fourths of all the land surface in the 
world lies in the northern hemisphere. As 
man’s home is always on the land, this is one 
reason why the northern hemisphere is more 
densely inhabited than the southern. Another 
reason is that the climate of the northern hemi¬ 
sphere is suited to a great number of activities, 
while the southern hemisphere which has a 
much more uniform climate offers fewer occu¬ 
pations for its inhabitants. 

The northern hemisphere is more closely 
linked together than the southern. Islands form 
stepping stones and continents extend over vast 
areas. This has made it easier for men to spread 
out, to mingle with one another and to create 
flourishing cities. The vast stretches of water in 
the southern hemisphere have made expansion 
a forbidding thing and the people have kept 


Why arc there 
more people in 
the Northern 
Hemisphere 
than in the 
Southern? 


92 


HOW THE WORLD IS CHANGING 


How have moun¬ 
tains influenced 
men? 


What are 
mountain 
passes? 


to themselves, living an isolated and unprogres- 
sive life. Often primitive conditions exist. 

One of the greatest barriers that men must 
meet is the mountains of the earth. In the 
early days of exploration, mountains often 
changed the history of nationalities. In the 
story of America alone, we see that the Appa¬ 
lachian mountains stopped the English from 
invading the western plains of America and the 
part of the United States today that bears traces 
of English settlement lies to the east of this 
mountain range. 

The safety of nations often depends upon a 
mountain barrier at the border-line. Thus the 
Pyrenees, a massive range unbroken by passes, 
is a great fortification for France and Spain. 
The Alps, forming a barrier for several nations, 
are not as impregnable as the Pyrenees because 
they are broken by a number of passes and val¬ 
leys which form passage-ways across. 

A mountain pass is a natural opening, leading 
from one valley to another. It may have been 
caused by some movement of the earth’s crust, 


THE EFFECTS OF THE EARTH ON MAN 93 


or it may have been cut by a swift stream, a 
moving glacier, or some combination of harsh 
weathering forces. 

Mountain passes play an important role in 
the history of mankind. In times of war, they 
are the weak spots in the great natural fortifica¬ 
tions that the mountain range makes. Natur¬ 
ally it is here, then, that generals order their 
men. Famous mountain passes that have time 
and again been the strategic points in some 
great campaign are the Khyber Pass leading 
from India into Turkestan and Persia, the St. 
Bernard Pass in the Alps where Napoleon’s 
whole army poured into Italy from France. In 
the famous French epic, “The Song of Roland,” 
Roland is supposed to meet his death at the pass 
of Roncesvalles where the Saracens crossed the 
Pyrenees. 

Mountain passes offer a more helpful aid to 
explorers and pioneers. The South Pass in the 
Rockies was a gateway to the Pacific in the days 
of western settlement. 

A mountain pass may decide a trade route. 


94 


HOW THE WORLD IS CHANGING 


What do the 
mountains 
offer men? 


The Mohawk Pass is the grain route from the 
northwest to the Atlantic seaboard. 

Offsetting the difficulties of life on a moun¬ 
tain slope, are certain great advantages. The 
mountains offer men, first of all, protection. 
After that there are numerous practical gifts 
that make life richer. The most valuable min¬ 
eral deposits are often found in mountainous 
regions. The valleys of mountain ranges arc 
usually fertile lands, easily cultivated. Certain 
mountain ranges are easily adapted to terracing 
so that farming is carried on upon the very 
slopes of the mountains. The grasslands of 
mountains are natural pasture grounds and the 
Swiss Alps and other ranges are famous as 
grazing ground. There are valuable forest pre¬ 
serves in mountainous regions. Lumbering is 
however a more difficult feat on the highlands 
and so much of the timber of the mountains has 
been left untouched. 

Mountain streams provide reservoirs of water 
for water power and irrigation and use in cities 
near-by. 



The grasslands of mountains are natural pasture 
lands 


95 











THE EFFECT OF THE EARTH ON MAN 97 


Far back when the world began and land 
was shaped by the infall of star dust and by the 
great movements of the earth, certain flat 
stretches of land were formed. These were the 
plains of the earth and were to be in time the 
principal home of mankind. 

Life on the plains is the easiest life that the 
earth offers. Here is an open countryside with 
no barriers to keep back expansion. Roads lend 
themselves easily to a smooth flat surface. The 
soils of plains are usually rich and deep. They 
are the ideal location for cities because there is 
room for many people to spread out easily. 

There are coastal plains and inland plains, 
desert plains and the famous steppes of Russia. 
There are flood plains caused by overflowing 
rivers, glacial plains caused by the deposits or 
drift of a glacier as it moves over the earth, 
leaving the material it has dragged with it 
behind. 

Valleys have always attracted men to settle 
in their fertile hollows. Usually a valley con¬ 
tains a river, and nearly all transportation in 


What is the 
importance of 
of the lowlands? 


What \inds of 
plains are there? 


How have valleys 
ta\en part in 
human history? 


98 


HOW THE WORLD IS CHANGING 


What role does 
an island play? 


the world follows a waterway. Also the valleys 
are the highways through plateaus or the 
bridges between land and sea. An old valley 
is more suited to agriculture than a young val¬ 
ley because it is wider and usually is character¬ 
ized by a wide and gentle river rather than a 
narrow rushing stream of water. 

Islands have long formed a thrilling back¬ 
ground for stories of adventure. “Treasure 



Islands have tempted men to explore—to leave the 
security of the mainland 


Island,” by Robert Louis Stevenson, is a classic. 
An island is an interesting settlement to study 
for it retains its apartness in all forms of its 












THE EFFECT OF THE EARTH ON MAN 


99 


society and culture as well as geographically. 
Its inhabitants are independent and highly 
individual. 

Islands off the coast are very often parts 
of the continent near which they are located. 
Some natural force separated them. The 
British Isles were once a part of the continent 
of Europe it is reasonably supposed. Often a 
coastal island forms a fine guard, standing be¬ 
tween the continent and the open sea as a sort 
of watchdog. 

Islands farther out in the ocean have played 
an interesting role in human affairs. They have 
tempted men to explore—to leave the security 
of the mainland for the uncertain horizons that 
lie beyond the seas. In ancient times the sturdy 
Vikings ventured forth, crossing to islands that 
were like stepping stones to encourage them, 
the Orkneys, Shetlands, Hebrides, from which 
they journeyed on to Iceland and even farther 
to the far continent of America. 

The largest city of most of the continents in 
the world is located on the coast, where it sur- 


100 


HOW THE WORLD IS CHANGING 


Where is the 
most important 
city on nearly 
every continent 
located? 


What is the 
advantage of a 
drowned coast? 


How does the 
soil direct man s 
activity? 


veys incoming and outgoing trade. New York 
is the gateway to the vast stretch of territory 
lying west of the ocean; in South America 
Buenos Aires holds this strategic position; 
London opens the door of Europe, Calcutta of 
Asia, and Sidney of Australia. 

With the sinking of certain lands came the 
drowning of valleys as well as highlands. A 
drowned valley usually formed a bay, and a bay 
is an advantageous place for a city to grow up 
around. Bays are easily made into harbors 
and a harbor is an asset to any locality. The 
bay of San Francisco is an example and has 
been called the Golden Gate. Such a bay 
extends its arms to welcome voyagers and the 
fortunate city beside the bay is populated with 
a cosmopolitan inflow from distant parts of 
the world. 

The mantle rock of the earth is just as im¬ 
portant to man as the great layers of solid 
rock that support the world he has built. 
“Safe upon the solid rock the ugly houses 
stand”—but if it were not for the top layers 


THE EFFECT OF THE EARTH ON MAN ioi 

of soil man could not grow his food that he 
must have to live. Soil is the most important 
gift of the earth to man. Whether it is red, 
brown, or black soil; lumpy, or in dusty grains; 
the texture of sand or of clay, it becomes the 
tool of man for his own life-giving nourish¬ 
ment. He learns to water the soil that is dry 
and to fertilize the soil that is not fertile. He 
ploughs and he plants and the soil rewards his 
efforts. Agriculture may be carried on in 
mountains or plateaus, in plains or in valleys— 
but one requirement is necessary and that is soil. 

Someone once said that wherever an obstruc- How arc 
tion occurs, a city is born. Thus at the foot clUes horn? 
of a mountain there may be a flourishing little 
village. One of the most important locations 
of cities is the Fall line. This line is at that 
point where a stream flowing from old land to 
a newly formed coastal plain often forms a 
waterfall. At this waterfall, men had to stop 
their boats and carry their cargo above the 
falls and continue their way in smaller boats 
upstream. Cities developed at these places 


102 


HOW THE WORLD IS CHANGING 


What occupations 
does the earth 
offer man? 


where a shifting of cargo was necessary. Phila¬ 
delphia, Baltimore, Washington, and Rich¬ 
mond are examples. 

Great waterfalls which offered tremendous 
possibilities in the way of water power were 
the inspiration for flourishing cities like Minne¬ 
apolis and Niagara Falls. 

The great trails of pioneers followed the 
waterways of the country, and their settlements 
were nearly always near water. Thus rivers 
and lakes are always dotted with important 
cities. Chicago is an example of a lake city 
that is like a miniature sea port, and New 
Orleans on the Mississippi and the Gulf is a 
port of far-reaching influence. 

Farming, grazing, forestry and mining arc 
the chief industries offered by the lands of the 
earth and fishing is the gift of the seas. 

The danger to the forests is that they have 
been cut down to provide more agricultural 
lands in the past, and that lumbering has been 
carried on without thought of the diminishing 
supply of timber. 


t 

THE EFFECT OF THE EARTH ON MAN 103 

A forest conservation movement is doing 
much to preserve the forests that we have and 
to encourage the growth of new timberlands. 

It is estimated that about a half of the world’s 
population is engaged in agriculture. In the 
isolated lands extensive farming and cattle- 
raising on a large scale are carried on, while 
the fertile lands near large cities are used to 
grow supplies to meet smaller demands. 

Two thousand million tons of mineral re¬ 
sources are produced by the world every year. 
Coal probably represents about 70 per cent of 
this total. The whole represents a sum of 
$9,000,000,000 or so. 

Man cannot live without water, nor can any 
other growing thing on earth. Besides furnish¬ 
ing a priceless necessity, the waters provide a 
supply of food that many may not be dependent 
upon but at least enjoys. Fishing is an industry 
that is as yet undeveloped to its greatest extent. 
When the foods of the land become scarce, 
people will turn to the almost unlimited supplies 
of the oceans. 


What is life 

dependent 

upon? 


HOW THE WORLD IS CHANGING 


How did the 
ocean become 
a highway? 


104 

Long ago the ocean loomed before the eyes 
of men as an impregnable barrier. The 
thinkers of the day, calling upon their imagi¬ 
nations rather than their knowledge, peopled 
it with horrible sea monsters and had visions 
of endless seas that offered nothing but peril to 
courageous voyagers. But the day came when 
Europe could no longer travel to the Orient to 
buy spices and silks and teas, for the Turks 
held the three gateways of the southern and 
eastern routes. Cut off from her trade with 
the east, Europe turned toward the Atlantic, 
wondering if a ship might travel around the 
world to the westward and eventually come 
upon India. After these early voyages the 
terrors of the ocean began to lessen. Men 
found that storms might blow and waves 
rise high, but that supernatural animals did 
not appear and that if the ship was sturdy 
enough land was finally sighted. 

Today transportation on the ocean is a 
tremendous activity. Commerce has developed 
so that in the year 1927 the total trade of 


THE EFFECT OF THE EARTH ON MAN 105 


exportation and importation carried on by the 
United States amounted to nearly ten thousand 
million dollars. 

The ocean waters become rain waters. This 
is one more of the magic changes and trans¬ 
formations that are constantly going on in the 
world. By means of the heat of the sun, the 
water in the vast oceans of the earth evaporates. 
The wind carries this water vapor over the 
land. When the atmosphere cools, the water 
vapor becomes rain, dew, snow, sleet, or hail 
and returns to earth in its new form. By 
nature’s roundabout methods, this same ocean 
water, that has returned to the earth as rain, 
may become part of a stream and eventually 
flow back into the ocean again. 

In the long history of mankind, the natural 
waterways of lakes and rivers and the man¬ 
made canals have been of tremendous influence 
commercially. Where there are few railways, 
trade is dependent upon waterways, and even 
in advanced countries water travel is cheaper 
than train transportation. 


How does the 
ocean water 
the soil? 


What is the 
importance 
of waterways? 


io6 


HOW THE WORLD IS CHANGING 


What are the 
gifts of the 
inland waters? 


How does cli¬ 
mate affect man? 


Some of the great rivers of the world have 
amazing histories and large cities have grown 
up along their banks. The Amazon river in 
Brazil, the Nile in Egypt, the Rhine in Ger¬ 
many, the Mississippi in the United States are 
rivers connected with ocean traffic that have 
influenced the destinies and the wealth of great 
nations of the world. 

Besides yielding supplies of fish, salt and 
mineral waters are found in inland waters. 
Rivers are an aid to the lumbering industry 
for most of the logs are floated down to the 
mills from the forests. Water power used for 
electricity is developed in a stream of any 
importance. Irrigation methods utilize what¬ 
ever water is needed where it is at all available, 
but naturally very arid lands are without 
neighboring streams, so irrigation cannot 
always be introduced where it is most needed. 

Climate influences the mood of man and 
the growth of plants, the development of 
civilization and the great migratory movements 
of the world. In the northern hemisphere 




After these early voyages the terrors of the ocean 
began to lessen 


107 


































THE EFFECT OF THE EARTH ON MAN 109 


where the climate is variable, man becomes 
vigorous and progressive. He may plunge 
himself into different sorts of occupations. 
Contrarily in the southern hemisphere he is 
reduced to an inactive and indolent laziness 
by the extreme heat and must follow one or 
another industry throughout a lifetime. Even 
temporary climatic disturbances will cause 
migratory movements. The flooding of the 
Ohio river and Mississippi valleys discourage 
further settlements there. Just as people will 
hesitate to live at the foot of a living volcano, 
they will avoid flood countries. 

The United States has risen like a bright star 
among the nations of the world. The youngest 
of the great nations, this astonishing country 
has caught up with the older countries in its 
commercial and industrial life. 

The United States is the child of the world 
who was born with a silver spoon in its mouth. 
All the good fairies of the earth showered down 
gifts so that the young nation started forth 
under fortunate and blessed circumstances. 


Why is the 
United States 
the fortunate 
child of the 
earth? 


HO 


HOW TOE WORLD IS CHANGING 


The vast area of the country was the first 
gift. Expansion means development. Where 
people are packed together, there is the ad¬ 
vantage perhaps of intense loyalty to one 
another, but there is no room to enlarge and 
to grow. A small country is apt to be stunted 
materially and economically. 

The natural resources of America are un¬ 
limited. Whereas France must go elsewhere 
for her mineral supplies, the United States 
needs only to turn to a part of her vast area. 
Whereas Great Britain must import most of 
her foodstuffs, America can easily grow her 
own and supply other countries as well. 

The United States is able to remain a uni¬ 
fied whole in spite of two great mountain ranges 
which at first seemed to create division lines. 
Passes and transcontinental railways were de¬ 
veloped and utilized in order to maintain the 
unity that is essential to the health of any nation. 
Great harbors also serve for shipping interests. 

It is fortunate that the United States is a 
long way from Europe because it has had a 


THE EFFECT OF THE EARTH ON MAN hi 


chance to develop and strengthen itself without 
interference from foreign shores. It is too far 
away to be molested by the nations on the other 
side of the ocean. 

The climate of the United States is the most 
favorable possible. Although the country ex¬ 
tends over vast areas, it remains in the temperate 
zone. There are no extremes in temperature 
such as the northern parts of Canada must 
suffer or the hot lands below the equator. 

Its location is strategically important in re¬ 
lation to the whole world. Its reach as far 
west as the Pacific brings it into relation with 
the Far East. And its position on the Atlantic 
opposite Europe creates the impression that it 
has much to offer Europe if she will but come 
across the stretch of water that lies between. 
And Europe has come across. Her people have 
sought out the promised land. Her tradesmen 
have made agreements concerning exports and 
imports that have been very beneficial to the 
United States also. 

The whole world looks at this big nation, 


112 


HOW THE WORLD IS CHANGING 


rich in resources, Gargantuan in size, located 
by fate and good fortune in the most favored 
position on the globe. The United States has 
become a power because of the gifts that the 
earth gave her. 































